Several studies have associated occupational exposures with the subsequent development of disease in the exposed workers, but relatively little work has been done on the reproductive effects of various exposures. Deleterious reproductive effects may be manifested as children born with severe defects. In particular, congenital heart disease is of interest because, unlike lesions that are clearly genetically transmitted, prior research has indicated that certain lesions can result from exogenous agents, such as chemicals (eg, drugs) used during pregnancy and viruses (eg, rubella) contracted during pregnancy. This study proposes to investigate the feasibility of using a geographically defined birth population of congenital heart disease cases and compare them with a similarly defined random sample of normal controls for differences in parental occupations grouped according to possible exposures. A second set of controls with Down's Syndrome is included to control for bias of recall. The study uses a retrospective approach because the incidence of congenital heart defects, particularly tetralogy of Fallot and pulmonic stenosis with and without ventricular septal defect, is relatively rare. Primary interest would center on grouping parental occupations according to possible exposures to lead, anesthetic gases, and detergents. Other variables of interest to be included in the analyses are pregnancy history, smoking, alcohol, and drug use during pregnancy.